1. Field of the Invention
The present invention relates to a source driver circuit of a display device.
2. Description of the Related Art
An LCD device is thinner and lighter than a Cathode Ray Tube (CRT), and is widely used for an information processing device since the quality of the LCD device is gradually enhanced.
An active matrix LCD device has a plurality of active elements that are respectively connected to plural pixel electrodes arranged in a matrix. An active matrix LCD device has a contrast ratio higher than that of a passive matrix LCD device. As a result, an active matrix driver is commonly used for a color LCD device.
The TFT (Thin Film Transistor) is widely used as an active element connected to each pixel electrode of an active matrix LCD device. FIG. 1 is a block diagram showing a conventional active matrix LCD device disclosed in U.S. Pat. No. 6,407,729.
Referring to FIG. 1, the controller 100 receives video data and control signals, and outputs control signals SCON to the gate driver unit 140 and gray scale data DATA to the source driver 1000.
A power supply unit 110 receives an external power source, and generates a stable DC voltage to provide the stable DC voltage to the controller 100, a gray scale voltage generator 120, and a gate voltage generator 130. The gray scale voltage generator 120 provides a reference gray scale voltage VGR to the source driver 1000. The gate voltage generator 130 generates a turn-on voltage and a turn-off voltage to provide the turn-on and turn-off voltages to the gate driver 140.
The gate driver 140 and source driver 1000 include a plurality of gate driver ICs and a plurality of source driver ICs, respectively. The gray scale data ‘DATA’ determine a gray scale level for each of the pixels. The gate driver 140 receives control signals SCON from the controller 100, and the source driver 1000 receives the gray scale data ‘DATA’ from the controller 100.
The source driver 1000 supplies a liquid crystal panel 150 with a plurality of source driving signals, and the gate driver 140 supplies the liquid crystal panel 150 with a plurality of gate signals. The liquid crystal panel 150 has a plurality of TFTs (Thin Film Transistors) located in matrices of the panel 150. A source of the TFT receives one of the source driving signals, and a gate of the TFT receives one of the gate signals. The TFT has a storage capacitor Cs and a liquid crystal capacitor CLC coupled to a drain of the TFT.
In the event that one of the source lines of the liquid crystal panel 150 is disconnected, the entire panel may not operate normally since the source driving signal is not transmitted to a source line disconnected from the source driver IC. When one or two disconnected source lines of the display panel 150 are considered to be a failed source line, the production yield of the LCD panels may be significantly lowered.